Dictionary.net

The separation of particles from a suspension by passage through a filter with very fine pores. In ultrafiltration the separation is accomplished by convective transport; in DIALYSIS separation relies instead upon differential diffusion. Ultrafiltration occurs naturally and is a laboratory procedure. Artificial ultrafiltration of the blood is referred to as HEMOFILTRATION or HEMODIAFILTRATION (if combined with HEMODIALYSIS).

The separation of crystalloids from colloids by filtration, namely, under high pressure through porcelain or collodion filters. The crystalloids pass through, the colloids are held back.